ECTV infection in mice models the course of human smallpox. Our data provide evidence to substantiate historical data on the usefulness of postexposure vaccination with conventional VACV and the new candidate MVA to protect against fatal orthopoxvirus infections.

Poxviruses such as virulent vaccinia virus (VACV) strain

Cats were experimentally infected with cell culture-adapted feline foamy virus (FFV, spumaretrovirinae) isolate FUV. FFV was consistently recovered from peripheral blood leukocytes and throat samples of FFV-infected cats starting 2 to 3 weeks postinfection (p. i.), indicative of the establishment of persistent FFV infections. Viral persistence was established, even despite neutralizing antibodies that appeared early after infection. The humoral immune response toward FFV was quantitatively and qualitatively analyzed over time. FFV Gag-specific antibodies were first detected 2 weeks p. i. and increased further; reactivities to the other structural and nonstructural FFV proteins appeared slightly delayed. Reactivities against FFV Pol and Gag proteins were detectable by immunoblotting and radioimmunoprecipitation, whereas the latter techniques had to be employed for the unambiguous detection of FFV Env-, Bet-, and Bel 1-specific antibodies.

Replication-competent feline foamy or spuma virus (FFV) vectors were constructed and functionally tested. The unmodified FFV vector genome expressed by the strong human cytomegalovirus immediate early promoter encodes FFV particles that were replication-competent in cell cultures. Virus derived from the cloned FFV DNA replicated and persisted in experimentally infected cats similar to the FFV isolate FUV. A FFV vector partially deleted in the noncoding area of the U3 region was used to transduce the gene for the green fluorescent protein (Gfp) into cell cultures. Gfp was expressed either by an internal ribosomal entry site (IRES) or as C-terminal fusion protein linked to Bet that was recently shown to be essential for FFV replication. Whereas the genetic stability of the IRES-Gfp construct was comparably low, the Bet-Gfp fusion protein was detectable upon serial cell-free vector passages. However, genetic rearrangements also occurred leading to the concomitant loss of marker gene expression.